High strength copper alloy having an excellent formability and process for producing the same

ABSTRACT

A high strength copper alloy having excellent formability consisting of from 0.2 to 0.5 percent by weight of beryllium, from 2.0 to 12.0 percent by weight of aluminum, from 0.5 to 10.0 percent by weight of zinc and the remainder of copper is disclosed. The copper alloy disclosed can be produced by melting a copper-beryllium master alloy, aluminum, zinc and copper so as to provide the above specified composition, casting the alloy into an ingot, hot working the ingot at about 800*C, cold working the ingot into the specified dimension, and then subjecting it to solution annealing at a temperature of from 800*C to 950*C followed by hardening either by cold working or ageing.

United States Patent [1 1 Shibata et al.

[ Aug. 21, 1973 Yoshitsugu Mishlma, Tokyo, both of Japan [73] Assignee: NGK Insulators, Ltd., Aichi, Japan [22] Filed: Jan. 22, 1971 [211 App]. No.: 108,994

[30] Foreign Application Priority Data Sept. 2, 1970 Japan 45/76893 [56] References Cited UNITED STATES PATENTS 2/1968 Opie 75/157.5 8/1969 Watanabe 75/153 X FOREIGN PATENTS OR APPLICATIONS 519,902 4/ 1940 Great Britain 75/162 725,679 3/1955 Great Britain 75/157.5 1,085,407 10/1967 Great Britain 75/162 138,568 8/1934 Austria 75/162 Primary Examiner-Charles N. Lovell Attorney-Sughrue, Rothwell, Mion, Zinn & Macpeak 5 7] ABSTRACT A high strength copper alloy having excellent formability consisting of from 0.2 to 0.5 percent by weight of beryllium, from 2.0 to 12.0 percent by weight of aluminum, from 0.5 to 10.0 percent by weight of zinc and the remainder of copper is disclosed. The copper alloy disclosed can be produced by melting a copper-beryllium master alloy, aluminum, zinc and copper so as to provide the above specified composition, casting the alloy into an ingot, hot working the ingot at about 800C, cold working the ingot into the specified dimension, and then subjecting it to solution annealing at a temperature of from 800C to 950C followed by hardening either by cold working or ageing.

1 Claim, No Drawings HIGH STRENGTH COPPER ALLOY HAVING AN EXCELLENT FORMABILITY AND PROCESS FOR PRODUCING THE SAME BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a high strength copper alloy having an excellent formability, and to a process for producing the same.

2. Description of the Prior Art Heretofore, brass, nickel silver, phosphor bronze, beryllium copper and the like have generally been used as copper alloys for spring use, and these alloys have been utilized industrially depending upon their respective characteristics.

Among the copper alloys, phosphor bronze has wide application for spring use because of its suitable characteristics and availability on the market. However, it has the disadvantage that any attempt to improve its spring properties results in poor formability. Therefore, a phosphor bronze having good spring properties cannot be formed satisfactorily. Beryllium copper has not been used widely because of the difficulty of its use from a commercial standpoint.

It is therefore the primary object of the present invention to provide a high strength copper alloy having excellent formability.

It is another object of the present invention to provide a method of producing a high strength copper alloy having excellent formability.

It is further an object of the present invention to provide a beryllium containing copper alloy which is easy to use from a commercial standpoint.

Various other objects and advantages of the present invention will become apparent to those skilled in the art on reading the accompanying description and disclosure.

SUMMARY OF THE INVENTION The present invention provides a high strength copper alloy having an excellent formability. The alloy consists of from 0.2 to 0.5 percent by weight of beryllium, from 2.0 to 12.0 percent by weight of aluminum, from 0.5 to 10.0 percent by weight of zinc and the remainder of copper.

The high strength copperv alloy, according to the present invention, is produced by melting a copperberyllium alloy, for example, a copper-4 percent beryllium master alloy, aluminum, zinc and copper in amounts to provide the above-specified composition, casting the alloy into an ingot, hot working the ingot at around 800C, cold working the alloy into the specified dimensions, and then subjecting the alloy to solution annealing at a temperature of from 800 to 950C followed by a hardening either by cold working or ageing.

DETAILED DESCRIPTION OF THE INVENTION When the amounts of beryllium, aluminum and zinc are less than 0.2 percent by weight, 2.0 percent by weight, and 0.5 percent by weight, respectively, the spring properties and ultimate tensile strength of the resulting alloy are poor.

When the amount of beryllium exceeds 0.5 percent by weight, the spring characteristics are further improved, but the formability is reduced to an unacceptable level.

When the amount of aluminum exceeds 12.0 percent by weight, the resulting alloy is poor in formability, and it is difficult to cold work the material.

When the amount of zinc exceeds 10.0 percent by weight, the resistance to stress corrosion of the resulting alloy is so poor as to be unacceptable.

Only by employing from 0.2 to 0.5 percent by weight of beryllium, from 2.0 to 12.0 percent by weight of aluminum, from 0.5 to 10.0 percent by weight of zinc and the remainder of copper, a high strength copper alloy which possesses more excellent formability and better spring properties than phosphor bronze can be obtained.

Although the melting temperatures are not critical, suitable melting temperatures are in the range of from I, l 00-l ,200C.

The times for solution annealing and ageing in the above-described process will be dependent upon the bulk and size of the alloy composition prepared.

When the quarternary alloy of Cu-Be-Al-Zn of the above-specified composition is produced, the agehardening of beryllium and the solid solution hardening of copper by zinc act together to strengthen the copper matrix. On cold working, the alloy shows considerable work hardening due to the large amount of solute elements.

Eutectoid decomposition in the Cu-Al system plays a role in strengthening the alloy as well. Consequently, upon heat-treatment, ageing and eutectoid transformation occur concurrently, and the copper is considerably strengthened by the dispersion of mixed precipitates.

Most of the alloying elements present in commercial copper alloys have no injurious effect on this alloy when they are introduced through the alloy scrap used in the preparation of the alloy.

The spring properties and formability of the alloys of the present invention have been compared with those of a conventional phosphor bronze, and the comparative data obtained are given in Table l below.

TABLE 1 Properties Formability Alloys (tensile elongation;'%) Remarks Present Invention 30.0 Cold Worked Present Invention 20.0 Cold Worked and Aged Conventional Phosphor Bronze 9 Spring Hard Temper As can be seen from Table l, the copper alloy of the present invention does not have the disadvantage of the conventional phosphor bronze of poor formability when fully hardened, and possessesexcellent formability. The price, however, is competitive with phosphor bronze.

The present invention will be further explained by reference to the following Examples which are merely illustrative and are not intended to be interpreted as limiting the invention.

EXAMPLES l-9 A 4% Be-Cu master alloy, aluminum ingot, zinc ingot, and cathode copper were prepared so that the beryllium, aluminum and zinc chemical composition as indicated in Table 2 was obtained. The cathode copper was melted in air together with the Cu-Be master alloy and the aluminum and zinc were added to the molten copper. The composition was mixed and cast into a graphite mold. The ingot thus obtained was scalfed on both surfaces and then hot forged at 800C into a slab, after which the slab was cold rolled to a moderate thickness, e.g., about 2 millimeters, with intermediate gular shape is needed, the alloy of the invention can be formed prior to the hardening treatment. Furthermore, since the alloy possesses a considerable elongation even after it is hardened, it still can be formed to the annealing at 800C Thereafter, the Slab was Subjected 5 same extent as is possible with fully hardened phosphor to solution annealing at 800C, 900C, 950C, bronze. Another advantage of the alloy of the invention Spectively, and cold rolled 20 Percent, 50 Percent of 80 is that it can be hot forged and hot rolled, and therefore Percent to Produce a sheet of the desired thlcknessthis can lead to an increased production efficiency over Ageing treatment was carried out at 300C phosphor bronze which cannot be hot formed. 350C or 400C. The properties of the alloy were mea- 10 V sured. The processing conditions and the properties of Thus, e c ppe a loy of the present invention 18 a the product obtained are given i T m 2 commercially advantageous alloy that possesses suffi- TABLE 2 Characteristic values Chemical composition (weight Solution annealing Ageing percent) Cold Tensile Tom era- Time rolling Tempera- Time strength Vickers Al Zn Cu ture 0.) (hrs.) (percent) ture 0.) (hrs.) (kgJmmfl) hardness 6.20 1.41 Remainder. 950 3 80 250 2 9L0 329 4. 20 950 1 50 300 2 92. 7 237 3.7a 800 2 so 350 a 85.5 282 5.70 2 80 400 1 69.0 246 1.92 800 3 50 300 3 77.7 277 3. s4 950 2 20 300 3 73.8 277 0. 20 900 1 so 300 3 81.5 329 10.20 800 1 20 300 2 95.2 302 See the following table:

Characteristic values Tensile strength Vickers (kg/mm hardness d b Spring hard Ph lat h t, t nd mile at osphor bronze p e s 86 S ASTM E 1 59.5-70 196-223 Alloy c 48. 3-58. s 125-196 It is clear from the results shown in Table 2 that with increasing cold reduction, the tensile strength and the hardness of the alloys of the present invention exceed those of phosphor bronze and even approach those of beryllium copper. When only the characteristics similar to those of phosphor bronze are desired, the reduction ratio should be made lower, a level of about 20 percent is sufficient, and thus outstanding formability even after hardening can be utilized.

Since the alloy of the present invention is of a hardenable type, it has low hardness and good elongation before hardening, and therefore is easily processed. When a complicated shape or highly contoured or ancient spring properties and tensile strength, superior to that of phosphor bronze.

While the present invention has been shown and described in certain forms only, it will be obvious to those skilled in the art that it is not so limited but is susceptible of various changes and modifications without departing from the spirit and scope thereof.

What is claimed is:

l. A high strength copper alloy having good spring properties and excellent formability consisting of from 0.2 to 0.5 percent by weight of beryllium, from 2.0 to 12.0 percent by weight of aluminum, and from 0.5 to 10.0 percent by weight of zinc, with the remainder of the alloy being copper.

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